Conventionally, there is a seat cushion adjusting apparatus capable of adjusting a length (longitudinal length) of a seat cushion based on an axial movement of a screw shaft screwed to a nut member. For example, a configuration, in which a nut member is driven to be rotated by an actuator supported by a frame of a seat cushion, is disclosed in JP 2011-15867A (Reference 1). In addition, a configuration, in which a screw shaft is driven to be rotated by an actuator supported on a movable side of a cushion length variable mechanism, is disclosed in US 2009/0033134A (Reference 2). That is, in these cushion length variable mechanisms, the screw shaft is moved in the seat longitudinal direction, i.e., in the length direction of the seat cushion, based on a screw relationship (screw pairing) between the screw shaft and the nut member. Then, according to this movement, a seating surface of the seat cushion is extended to the front side and retracted to the rear side, thereby the length of the seat cushion is changed.
However, in the seat cushion adjusting apparatus described above, one end of the screw shaft is depressed based on a seat load acting on a front end portion of the seat cushion and thereby an axis of the screw shaft may be inclined with respect to an axis of the nut member. Then, there is a concern that a smooth operation of the cushion length variable mechanism is hindered by an increase in frictional resistance generated thereby. In this regard, it leaves room for improvement.